Would Hood sinking Bismarck in an explosion that killed everyone aboard have been enough to cancel HMS Vanguard?
Short answerNo. Vanguard would still have been built, although she might have been delayed or redesigned with 16-inch guns.
NotesHMS Vanguard would still have been built if Hood had sunk Bismarck in an explosion that killed everyone aboard the German battleship. A lengthy delay remains possible in this counterfactual. Another possibility is a change to 16-inch guns.